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CVE-2026-89639

7.1 · HIGH

In the Linux kernel, the following vulnerability has been resolved: cifs: use cifs_invalidate_cache() in cifs_do_truncate() for O_TRUNC cifs_do_truncate() is invoked from cifs_open() without i_rw…

Published Sep 11, 2026EPSS 0.13%

Overview

CVE-2026-89639 is a high-severity vulnerability. It was published on September 11, 2026 and has a CVSS 3.1 base score of 7.1 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.1, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

Technical description

In the Linux kernel, the following vulnerability has been resolved:

cifs: use cifs_invalidate_cache() in cifs_do_truncate() for O_TRUNC

cifs_do_truncate() is invoked from cifs_open() without i_rwsem, so it

cannot use cifs_resize_file_locked() to perform a proper fscache cookie

resize. Instead, add cifs_invalidate_cache() after cifs_setsize().

cifs_invalidate_cache() calls fscache_invalidate(), which works without

holding i_rwsem: it unconditionally increments inval_counter and sets

FSCACHE_COOKIE_NO_DATA_TO_READ, ensuring that stale cached data is not

served once the cookie is later activated by fscache_use_cookie().

Truncation to zero leaves no valid cached data, making invalidation the

correct semantic here.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/364b183230586a62660a7280c1eb20138338eeb5Refgit.kernel.org/stable/c/81fc3868a7f726980ff845c1d0d271051e5f0f45Refgit.kernel.org/stable/c/8b9b10fe5b8b492b27b9f4546742ea541a650213

How CyberStrike helps

Frequently asked questions

What is CVE-2026-89639?

CVE-2026-89639 is a high-severity vulnerability. It was published on September 11, 2026 and has a CVSS 3.1 base score of 7.1 (HIGH).

How severe is CVE-2026-89639?

This vulnerability has a CVSS 3.1 base score of 7.1, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2026-89639?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-89639?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-89639 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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